This invention relates generally to blind fastener members, generally of a three piece variety, and which are adapted to be inserted through an aperture in a workpiece and anchored therein with access to only one side of the workpiece. Such a fastener typically includes a threaded fastener having a shank and a head, a sleeve with a through bore and including a head at one end, and an expansion member designed to expand radially outwardly as it is pulled over the sleeve by the rotation of the threaded fastener.
Prior art devices of this general type are generally inadequate because of the lack of positive restraint of relative rotation between the expansion member and the sleeve. If the expansion member is permitted to rotate relative to the sleeve, then there will be no telescopic movement over the sleeve and thus eliminates effective expansion of the device on the blind side of the workpiece.
Prior art devices also typically are deficient in providing firm, distributed clamping pressure on the blind side of the workpieces. A distribution of the clamping forces is important in such a fastening technique to prevent the nut or expansion member from being pulled through the aperture under increasing clamping pressure.